Saltwater crocodile is the largest crocodile species.This species of crocodile can grow up to a length of 7 meters or 23 feet and weigh up to 1 tonne approx. A crocodile can't move its tongue but held in place by a membrane which limits movement.Crocodiles do not have sweat glands and release heat through their mouths.The first crocodiles appeared on earth, around 240 million years ago, around the same time as dinosaurs.

They often sleep with their mouths open and may even pant like a dog.Crocodiles, like all reptiles have a retina that is populated mostly by cone photo-receptors. Alligators and caiman's have colour vision, and it is likely that all crocodiles have it. Crocodile's vision is blurred when the membrane covers the eye.

There are different types of cones, each sensitive to a different wavelength "color", and the cones themselves have oil droplets that further filter the light that comes through.

Can Crocodiles walk on their tails? If they are being threatened , crocodiles can move so fast that they almost leap out of the water. This is called 'tail-walking'.